Cursor.__deepcopy() does not support lists and causes (obscure) application crashes

The method pymongo.cursor.Cursor.__deepcopy() was apparently created avoid copying regex'es in a deep copy. It works to copy dicts but does nothing for the list case. I found this behavior to be the cause of (obscure) "cannot deepcopy this pattern object" crashes when using Flask-admin with mongoengine. The failure was the result of query criteria containing a list that contained regex'es. In that list case __deepcopy() just calls copy.deepcopy() which fails on the regex'es.

The submitted patch enables __deepcopy to copy lists in addition to dicts. My goal in writing the patch was to implement the list case while minimizing logic changes to the original code as I did not want to unintentionally introduce any new problems. So the code may appear a bit clumsy. But it is perfectly functional and solves the failing case.

I hope this helps. Thanks for all the good work! -Juan